/*
 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package javax.swing;

import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.beans.*;
import java.lang.reflect.*;
import java.io.*;
import java.util.TooManyListenersException;
import javax.swing.plaf.UIResource;
import javax.swing.event.*;
import javax.swing.text.JTextComponent;

import sun.reflect.misc.MethodUtil;
import sun.swing.SwingUtilities2;
import sun.awt.AppContext;
import sun.swing.*;
import sun.awt.SunToolkit;

import java.security.AccessController;
import java.security.PrivilegedAction;

import java.security.AccessControlContext;
import java.security.ProtectionDomain;
import sun.misc.SharedSecrets;
import sun.misc.JavaSecurityAccess;

import sun.awt.AWTAccessor;

/**
 * This class is used to handle the transfer of a <code>Transferable</code>
 * to and from Swing components.  The <code>Transferable</code> is used to
 * represent data that is exchanged via a cut, copy, or paste
 * to/from a clipboard.  It is also used in drag-and-drop operations
 * to represent a drag from a component, and a drop to a component.
 * Swing provides functionality that automatically supports cut, copy,
 * and paste keyboard bindings that use the functionality provided by
 * an implementation of this class.  Swing also provides functionality
 * that automatically supports drag and drop that uses the functionality
 * provided by an implementation of this class.  The Swing developer can
 * concentrate on specifying the semantics of a transfer primarily by setting
 * the <code>transferHandler</code> property on a Swing component.
 * <p>
 * This class is implemented to provide a default behavior of transferring
 * a component property simply by specifying the name of the property in
 * the constructor.  For example, to transfer the foreground color from
 * one component to another either via the clipboard or a drag and drop operation
 * a <code>TransferHandler</code> can be constructed with the string "foreground".  The
 * built in support will use the color returned by <code>getForeground</code> as the source
 * of the transfer, and <code>setForeground</code> for the target of a transfer.
 * <p>
 * Please see
 * <a href="https://docs.oracle.com/javase/tutorial/uiswing/dnd/index.html">
 * How to Use Drag and Drop and Data Transfer</a>,
 * a section in <em>The Java Tutorial</em>, for more information.
 *
 * @author Timothy Prinzing
 * @author Shannon Hickey
 * @since 1.4
 */
@SuppressWarnings("serial")
public class TransferHandler implements Serializable {

  /**
   * An <code>int</code> representing no transfer action.
   */
  public static final int NONE = DnDConstants.ACTION_NONE;

  /**
   * An <code>int</code> representing a &quot;copy&quot; transfer action.
   * This value is used when data is copied to a clipboard
   * or copied elsewhere in a drag and drop operation.
   */
  public static final int COPY = DnDConstants.ACTION_COPY;

  /**
   * An <code>int</code> representing a &quot;move&quot; transfer action.
   * This value is used when data is moved to a clipboard (i.e. a cut)
   * or moved elsewhere in a drag and drop operation.
   */
  public static final int MOVE = DnDConstants.ACTION_MOVE;

  /**
   * An <code>int</code> representing a source action capability of either
   * &quot;copy&quot; or &quot;move&quot;.
   */
  public static final int COPY_OR_MOVE = DnDConstants.ACTION_COPY_OR_MOVE;

  /**
   * An <code>int</code> representing a &quot;link&quot; transfer action.
   * This value is used to specify that data should be linked in a drag
   * and drop operation.
   *
   * @see java.awt.dnd.DnDConstants#ACTION_LINK
   * @since 1.6
   */
  public static final int LINK = DnDConstants.ACTION_LINK;

  /**
   * An interface to tag things with a {@code getTransferHandler} method.
   */
  interface HasGetTransferHandler {

    /**
     * Returns the {@code TransferHandler}.
     *
     * @return The {@code TransferHandler} or {@code null}
     */
    public TransferHandler getTransferHandler();
  }

  /**
   * Represents a location where dropped data should be inserted.
   * This is a base class that only encapsulates a point.
   * Components supporting drop may provide subclasses of this
   * containing more information.
   * <p>
   * Developers typically shouldn't create instances of, or extend, this
   * class. Instead, these are something provided by the DnD
   * implementation by <code>TransferSupport</code> instances and by
   * components with a <code>getDropLocation()</code> method.
   *
   * @see javax.swing.TransferHandler.TransferSupport#getDropLocation
   * @since 1.6
   */
  public static class DropLocation {

    private final Point dropPoint;

    /**
     * Constructs a drop location for the given point.
     *
     * @param dropPoint the drop point, representing the mouse's current location within the
     * component.
     * @throws IllegalArgumentException if the point is <code>null</code>
     */
    protected DropLocation(Point dropPoint) {
      if (dropPoint == null) {
        throw new IllegalArgumentException("Point cannot be null");
      }

      this.dropPoint = new Point(dropPoint);
    }

    /**
     * Returns the drop point, representing the mouse's
     * current location within the component.
     *
     * @return the drop point.
     */
    public final Point getDropPoint() {
      return new Point(dropPoint);
    }

    /**
     * Returns a string representation of this drop location.
     * This method is intended to be used for debugging purposes,
     * and the content and format of the returned string may vary
     * between implementations.
     *
     * @return a string representation of this drop location
     */
    public String toString() {
      return getClass().getName() + "[dropPoint=" + dropPoint + "]";
    }
  }

  ;

  /**
   * This class encapsulates all relevant details of a clipboard
   * or drag and drop transfer, and also allows for customizing
   * aspects of the drag and drop experience.
   * <p>
   * The main purpose of this class is to provide the information
   * needed by a developer to determine the suitability of a
   * transfer or to import the data contained within. But it also
   * doubles as a controller for customizing properties during drag
   * and drop, such as whether or not to show the drop location,
   * and which drop action to use.
   * <p>
   * Developers typically need not create instances of this
   * class. Instead, they are something provided by the DnD
   * implementation to certain methods in <code>TransferHandler</code>.
   *
   * @see #canImport(TransferHandler.TransferSupport)
   * @see #importData(TransferHandler.TransferSupport)
   * @since 1.6
   */
  public final static class TransferSupport {

    private boolean isDrop;
    private Component component;

    private boolean showDropLocationIsSet;
    private boolean showDropLocation;

    private int dropAction = -1;

    /**
     * The source is a {@code DropTargetDragEvent} or
     * {@code DropTargetDropEvent} for drops,
     * and a {@code Transferable} otherwise
     */
    private Object source;

    private DropLocation dropLocation;

    /**
     * Create a <code>TransferSupport</code> with <code>isDrop()</code>
     * <code>true</code> for the given component, event, and index.
     *
     * @param component the target component
     * @param event a <code>DropTargetEvent</code>
     */
    private TransferSupport(Component component,
        DropTargetEvent event) {

      isDrop = true;
      setDNDVariables(component, event);
    }

    /**
     * Create a <code>TransferSupport</code> with <code>isDrop()</code>
     * <code>false</code> for the given component and
     * <code>Transferable</code>.
     *
     * @param component the target component
     * @param transferable the transferable
     * @throws NullPointerException if either parameter is <code>null</code>
     */
    public TransferSupport(Component component, Transferable transferable) {
      if (component == null) {
        throw new NullPointerException("component is null");
      }

      if (transferable == null) {
        throw new NullPointerException("transferable is null");
      }

      isDrop = false;
      this.component = component;
      this.source = transferable;
    }

    /**
     * Allows for a single instance to be reused during DnD.
     *
     * @param component the target component
     * @param event a <code>DropTargetEvent</code>
     */
    private void setDNDVariables(Component component,
        DropTargetEvent event) {

      assert isDrop;

      this.component = component;
      this.source = event;
      dropLocation = null;
      dropAction = -1;
      showDropLocationIsSet = false;

      if (source == null) {
        return;
      }

      assert source instanceof DropTargetDragEvent ||
          source instanceof DropTargetDropEvent;

      Point p = source instanceof DropTargetDragEvent
          ? ((DropTargetDragEvent) source).getLocation()
          : ((DropTargetDropEvent) source).getLocation();

      if (SunToolkit.isInstanceOf(component, "javax.swing.text.JTextComponent")) {
        dropLocation = SwingAccessor.getJTextComponentAccessor().
            dropLocationForPoint((JTextComponent) component, p);
      } else if (component instanceof JComponent) {
        dropLocation = ((JComponent) component).dropLocationForPoint(p);
      }

            /*
             * The drop location may be null at this point if the component
             * doesn't return custom drop locations. In this case, a point-only
             * drop location will be created lazily when requested.
             */
    }

    /**
     * Returns whether or not this <code>TransferSupport</code>
     * represents a drop operation.
     *
     * @return <code>true</code> if this is a drop operation, <code>false</code> otherwise.
     */
    public boolean isDrop() {
      return isDrop;
    }

    /**
     * Returns the target component of this transfer.
     *
     * @return the target component
     */
    public Component getComponent() {
      return component;
    }

    /**
     * Checks that this is a drop and throws an
     * {@code IllegalStateException} if it isn't.
     *
     * @throws IllegalStateException if {@code isDrop} is false.
     */
    private void assureIsDrop() {
      if (!isDrop) {
        throw new IllegalStateException("Not a drop");
      }
    }

    /**
     * Returns the current (non-{@code null}) drop location for the component,
     * when this {@code TransferSupport} represents a drop.
     * <p>
     * Note: For components with built-in drop support, this location
     * will be a subclass of {@code DropLocation} of the same type
     * returned by that component's {@code getDropLocation} method.
     * <p>
     * This method is only for use with drag and drop transfers.
     * Calling it when {@code isDrop()} is {@code false} results
     * in an {@code IllegalStateException}.
     *
     * @return the drop location
     * @throws IllegalStateException if this is not a drop
     * @see #isDrop()
     */
    public DropLocation getDropLocation() {
      assureIsDrop();

      if (dropLocation == null) {
                /*
                 * component didn't give us a custom drop location,
                 * so lazily create a point-only location
                 */
        Point p = source instanceof DropTargetDragEvent
            ? ((DropTargetDragEvent) source).getLocation()
            : ((DropTargetDropEvent) source).getLocation();

        dropLocation = new DropLocation(p);
      }

      return dropLocation;
    }

    /**
     * Sets whether or not the drop location should be visually indicated
     * for the transfer - which must represent a drop. This is applicable to
     * those components that automatically
     * show the drop location when appropriate during a drag and drop
     * operation). By default, the drop location is shown only when the
     * {@code TransferHandler} has said it can accept the import represented
     * by this {@code TransferSupport}. With this method you can force the
     * drop location to always be shown, or always not be shown.
     * <p>
     * This method is only for use with drag and drop transfers.
     * Calling it when {@code isDrop()} is {@code false} results
     * in an {@code IllegalStateException}.
     *
     * @param showDropLocation whether or not to indicate the drop location
     * @throws IllegalStateException if this is not a drop
     * @see #isDrop()
     */
    public void setShowDropLocation(boolean showDropLocation) {
      assureIsDrop();

      this.showDropLocation = showDropLocation;
      this.showDropLocationIsSet = true;
    }

    /**
     * Sets the drop action for the transfer - which must represent a drop
     * - to the given action,
     * instead of the default user drop action. The action must be
     * supported by the source's drop actions, and must be one
     * of {@code COPY}, {@code MOVE} or {@code LINK}.
     * <p>
     * This method is only for use with drag and drop transfers.
     * Calling it when {@code isDrop()} is {@code false} results
     * in an {@code IllegalStateException}.
     *
     * @param dropAction the drop action
     * @throws IllegalStateException if this is not a drop
     * @throws IllegalArgumentException if an invalid action is specified
     * @see #getDropAction
     * @see #getUserDropAction
     * @see #getSourceDropActions
     * @see #isDrop()
     */
    public void setDropAction(int dropAction) {
      assureIsDrop();

      int action = dropAction & getSourceDropActions();

      if (!(action == COPY || action == MOVE || action == LINK)) {
        throw new IllegalArgumentException("unsupported drop action: " + dropAction);
      }

      this.dropAction = dropAction;
    }

    /**
     * Returns the action chosen for the drop, when this
     * {@code TransferSupport} represents a drop.
     * <p>
     * Unless explicitly chosen by way of {@code setDropAction},
     * this returns the user drop action provided by
     * {@code getUserDropAction}.
     * <p>
     * You may wish to query this in {@code TransferHandler}'s
     * {@code importData} method to customize processing based
     * on the action.
     * <p>
     * This method is only for use with drag and drop transfers.
     * Calling it when {@code isDrop()} is {@code false} results
     * in an {@code IllegalStateException}.
     *
     * @return the action chosen for the drop
     * @throws IllegalStateException if this is not a drop
     * @see #setDropAction
     * @see #getUserDropAction
     * @see #isDrop()
     */
    public int getDropAction() {
      return dropAction == -1 ? getUserDropAction() : dropAction;
    }

    /**
     * Returns the user drop action for the drop, when this
     * {@code TransferSupport} represents a drop.
     * <p>
     * The user drop action is chosen for a drop as described in the
     * documentation for {@link java.awt.dnd.DropTargetDragEvent} and
     * {@link java.awt.dnd.DropTargetDropEvent}. A different action
     * may be chosen as the drop action by way of the {@code setDropAction}
     * method.
     * <p>
     * You may wish to query this in {@code TransferHandler}'s
     * {@code canImport} method when determining the suitability of a
     * drop or when deciding on a drop action to explicitly choose.
     * <p>
     * This method is only for use with drag and drop transfers.
     * Calling it when {@code isDrop()} is {@code false} results
     * in an {@code IllegalStateException}.
     *
     * @return the user drop action
     * @throws IllegalStateException if this is not a drop
     * @see #setDropAction
     * @see #getDropAction
     * @see #isDrop()
     */
    public int getUserDropAction() {
      assureIsDrop();

      return (source instanceof DropTargetDragEvent)
          ? ((DropTargetDragEvent) source).getDropAction()
          : ((DropTargetDropEvent) source).getDropAction();
    }

    /**
     * Returns the drag source's supported drop actions, when this
     * {@code TransferSupport} represents a drop.
     * <p>
     * The source actions represent the set of actions supported by the
     * source of this transfer, and are represented as some bitwise-OR
     * combination of {@code COPY}, {@code MOVE} and {@code LINK}.
     * You may wish to query this in {@code TransferHandler}'s
     * {@code canImport} method when determining the suitability of a drop
     * or when deciding on a drop action to explicitly choose. To determine
     * if a particular action is supported by the source, bitwise-AND
     * the action with the source drop actions, and then compare the result
     * against the original action. For example:
     * <pre>
     * boolean copySupported = (COPY &amp; getSourceDropActions()) == COPY;
     * </pre>
     * <p>
     * This method is only for use with drag and drop transfers.
     * Calling it when {@code isDrop()} is {@code false} results
     * in an {@code IllegalStateException}.
     *
     * @return the drag source's supported drop actions
     * @throws IllegalStateException if this is not a drop
     * @see #isDrop()
     */
    public int getSourceDropActions() {
      assureIsDrop();

      return (source instanceof DropTargetDragEvent)
          ? ((DropTargetDragEvent) source).getSourceActions()
          : ((DropTargetDropEvent) source).getSourceActions();
    }

    /**
     * Returns the data flavors for this transfer.
     *
     * @return the data flavors for this transfer
     */
    public DataFlavor[] getDataFlavors() {
      if (isDrop) {
        if (source instanceof DropTargetDragEvent) {
          return ((DropTargetDragEvent) source).getCurrentDataFlavors();
        } else {
          return ((DropTargetDropEvent) source).getCurrentDataFlavors();
        }
      }

      return ((Transferable) source).getTransferDataFlavors();
    }

    /**
     * Returns whether or not the given data flavor is supported.
     *
     * @param df the <code>DataFlavor</code> to test
     * @return whether or not the given flavor is supported.
     */
    public boolean isDataFlavorSupported(DataFlavor df) {
      if (isDrop) {
        if (source instanceof DropTargetDragEvent) {
          return ((DropTargetDragEvent) source).isDataFlavorSupported(df);
        } else {
          return ((DropTargetDropEvent) source).isDataFlavorSupported(df);
        }
      }

      return ((Transferable) source).isDataFlavorSupported(df);
    }

    /**
     * Returns the <code>Transferable</code> associated with this transfer.
     * <p>
     * Note: Unless it is necessary to fetch the <code>Transferable</code>
     * directly, use one of the other methods on this class to inquire about
     * the transfer. This may perform better than fetching the
     * <code>Transferable</code> and asking it directly.
     *
     * @return the <code>Transferable</code> associated with this transfer
     */
    public Transferable getTransferable() {
      if (isDrop) {
        if (source instanceof DropTargetDragEvent) {
          return ((DropTargetDragEvent) source).getTransferable();
        } else {
          return ((DropTargetDropEvent) source).getTransferable();
        }
      }

      return (Transferable) source;
    }
  }


  /**
   * Returns an {@code Action} that performs cut operations to the
   * clipboard. When performed, this action operates on the {@code JComponent}
   * source of the {@code ActionEvent} by invoking {@code exportToClipboard},
   * with a {@code MOVE} action, on the component's {@code TransferHandler}.
   *
   * @return an {@code Action} for performing cuts to the clipboard
   */
  public static Action getCutAction() {
    return cutAction;
  }

  /**
   * Returns an {@code Action} that performs copy operations to the
   * clipboard. When performed, this action operates on the {@code JComponent}
   * source of the {@code ActionEvent} by invoking {@code exportToClipboard},
   * with a {@code COPY} action, on the component's {@code TransferHandler}.
   *
   * @return an {@code Action} for performing copies to the clipboard
   */
  public static Action getCopyAction() {
    return copyAction;
  }

  /**
   * Returns an {@code Action} that performs paste operations from the
   * clipboard. When performed, this action operates on the {@code JComponent}
   * source of the {@code ActionEvent} by invoking {@code importData},
   * with the clipboard contents, on the component's {@code TransferHandler}.
   *
   * @return an {@code Action} for performing pastes from the clipboard
   */
  public static Action getPasteAction() {
    return pasteAction;
  }


  /**
   * Constructs a transfer handler that can transfer a Java Bean property
   * from one component to another via the clipboard or a drag and drop
   * operation.
   *
   * @param property the name of the property to transfer; this can be <code>null</code> if there is
   * no property associated with the transfer handler (a subclass that performs some other kind of
   * transfer, for example)
   */
  public TransferHandler(String property) {
    propertyName = property;
  }

  /**
   * Convenience constructor for subclasses.
   */
  protected TransferHandler() {
    this(null);
  }


  /**
   * image for the {@code startDrag} method
   *
   * @see java.awt.dnd.DragGestureEvent#startDrag(Cursor dragCursor, Image dragImage, Point
   * imageOffset, Transferable transferable, DragSourceListener dsl)
   */
  private Image dragImage;

  /**
   * anchor offset for the {@code startDrag} method
   *
   * @see java.awt.dnd.DragGestureEvent#startDrag(Cursor dragCursor, Image dragImage, Point
   * imageOffset, Transferable transferable, DragSourceListener dsl)
   */
  private Point dragImageOffset;

  /**
   * Sets the drag image parameter. The image has to be prepared
   * for rendering by the moment of the call. The image is stored
   * by reference because of some performance reasons.
   *
   * @param img an image to drag
   */
  public void setDragImage(Image img) {
    dragImage = img;
  }

  /**
   * Returns the drag image. If there is no image to drag,
   * the returned value is {@code null}.
   *
   * @return the reference to the drag image
   */
  public Image getDragImage() {
    return dragImage;
  }

  /**
   * Sets an anchor offset for the image to drag.
   * It can not be {@code null}.
   *
   * @param p a {@code Point} object that corresponds to coordinates of an anchor offset of the
   * image relative to the upper left corner of the image
   */
  public void setDragImageOffset(Point p) {
    dragImageOffset = new Point(p);
  }

  /**
   * Returns an anchor offset for the image to drag.
   *
   * @return a {@code Point} object that corresponds to coordinates of an anchor offset of the image
   * relative to the upper left corner of the image. The point {@code (0,0)} returns by default.
   */
  public Point getDragImageOffset() {
    if (dragImageOffset == null) {
      return new Point(0, 0);
    }
    return new Point(dragImageOffset);
  }

  /**
   * Causes the Swing drag support to be initiated.  This is called by
   * the various UI implementations in the <code>javax.swing.plaf.basic</code>
   * package if the dragEnabled property is set on the component.
   * This can be called by custom UI
   * implementations to use the Swing drag support.  This method can also be called
   * by a Swing extension written as a subclass of <code>JComponent</code>
   * to take advantage of the Swing drag support.
   * <p>
   * The transfer <em>will not necessarily</em> have been completed at the
   * return of this call (i.e. the call does not block waiting for the drop).
   * The transfer will take place through the Swing implementation of the
   * <code>java.awt.dnd</code> mechanism, requiring no further effort
   * from the developer. The <code>exportDone</code> method will be called
   * when the transfer has completed.
   *
   * @param comp the component holding the data to be transferred; provided to enable sharing of
   * <code>TransferHandler</code>s
   * @param e the event that triggered the transfer
   * @param action the transfer action initially requested; either {@code COPY}, {@code MOVE} or
   * {@code LINK}; the DnD system may change the action used during the course of the drag
   * operation
   */
  public void exportAsDrag(JComponent comp, InputEvent e, int action) {
    int srcActions = getSourceActions(comp);

    // only mouse events supported for drag operations
    if (!(e instanceof MouseEvent)
        // only support known actions
        || !(action == COPY || action == MOVE || action == LINK)
        // only support valid source actions
        || (srcActions & action) == 0) {

      action = NONE;
    }

    if (action != NONE && !GraphicsEnvironment.isHeadless()) {
      if (recognizer == null) {
        recognizer = new SwingDragGestureRecognizer(new DragHandler());
      }
      recognizer.gestured(comp, (MouseEvent) e, srcActions, action);
    } else {
      exportDone(comp, null, NONE);
    }
  }

  /**
   * Causes a transfer from the given component to the
   * given clipboard.  This method is called by the default cut and
   * copy actions registered in a component's action map.
   * <p>
   * The transfer will take place using the <code>java.awt.datatransfer</code>
   * mechanism, requiring no further effort from the developer. Any data
   * transfer <em>will</em> be complete and the <code>exportDone</code>
   * method will be called with the action that occurred, before this method
   * returns. Should the clipboard be unavailable when attempting to place
   * data on it, the <code>IllegalStateException</code> thrown by
   * {@link Clipboard#setContents(Transferable, ClipboardOwner)} will
   * be propagated through this method. However,
   * <code>exportDone</code> will first be called with an action
   * of <code>NONE</code> for consistency.
   *
   * @param comp the component holding the data to be transferred; provided to enable sharing of
   * <code>TransferHandler</code>s
   * @param clip the clipboard to transfer the data into
   * @param action the transfer action requested; this should be a value of either <code>COPY</code>
   * or <code>MOVE</code>; the operation performed is the intersection  of the transfer capabilities
   * given by getSourceActions and the requested action; the intersection may result in an action of
   * <code>NONE</code> if the requested action isn't supported
   * @throws IllegalStateException if the clipboard is currently unavailable
   * @see Clipboard#setContents(Transferable, ClipboardOwner)
   */
  public void exportToClipboard(JComponent comp, Clipboard clip, int action)
      throws IllegalStateException {

    if ((action == COPY || action == MOVE)
        && (getSourceActions(comp) & action) != 0) {

      Transferable t = createTransferable(comp);
      if (t != null) {
        try {
          clip.setContents(t, null);
          exportDone(comp, t, action);
          return;
        } catch (IllegalStateException ise) {
          exportDone(comp, t, NONE);
          throw ise;
        }
      }
    }

    exportDone(comp, null, NONE);
  }

  /**
   * Causes a transfer to occur from a clipboard or a drag and
   * drop operation. The <code>Transferable</code> to be
   * imported and the component to transfer to are contained
   * within the <code>TransferSupport</code>.
   * <p>
   * While the drag and drop implementation calls {@code canImport}
   * to determine the suitability of a transfer before calling this
   * method, the implementation of paste does not. As such, it cannot
   * be assumed that the transfer is acceptable upon a call to
   * this method for paste. It is recommended that {@code canImport} be
   * explicitly called to cover this case.
   * <p>
   * Note: The <code>TransferSupport</code> object passed to this method
   * is only valid for the duration of the method call. It is undefined
   * what values it may contain after this method returns.
   *
   * @param support the object containing the details of the transfer, not <code>null</code>.
   * @return true if the data was inserted into the component, false otherwise
   * @throws NullPointerException if <code>support</code> is {@code null}
   * @see #canImport(TransferHandler.TransferSupport)
   * @since 1.6
   */
  public boolean importData(TransferSupport support) {
    return support.getComponent() instanceof JComponent
        ? importData((JComponent) support.getComponent(), support.getTransferable())
        : false;
  }

  /**
   * Causes a transfer to a component from a clipboard or a
   * DND drop operation.  The <code>Transferable</code> represents
   * the data to be imported into the component.
   * <p>
   * Note: Swing now calls the newer version of <code>importData</code>
   * that takes a <code>TransferSupport</code>, which in turn calls this
   * method (if the component in the {@code TransferSupport} is a
   * {@code JComponent}). Developers are encouraged to call and override the
   * newer version as it provides more information (and is the only
   * version that supports use with a {@code TransferHandler} set directly
   * on a {@code JFrame} or other non-{@code JComponent}).
   *
   * @param comp the component to receive the transfer; provided to enable sharing of
   * <code>TransferHandler</code>s
   * @param t the data to import
   * @return true if the data was inserted into the component, false otherwise
   * @see #importData(TransferHandler.TransferSupport)
   */
  public boolean importData(JComponent comp, Transferable t) {
    PropertyDescriptor prop = getPropertyDescriptor(comp);
    if (prop != null) {
      Method writer = prop.getWriteMethod();
      if (writer == null) {
        // read-only property. ignore
        return false;
      }
      Class<?>[] params = writer.getParameterTypes();
      if (params.length != 1) {
        // zero or more than one argument, ignore
        return false;
      }
      DataFlavor flavor = getPropertyDataFlavor(params[0], t.getTransferDataFlavors());
      if (flavor != null) {
        try {
          Object value = t.getTransferData(flavor);
          Object[] args = {value};
          MethodUtil.invoke(writer, comp, args);
          return true;
        } catch (Exception ex) {
          System.err.println("Invocation failed");
          // invocation code
        }
      }
    }
    return false;
  }

  /**
   * This method is called repeatedly during a drag and drop operation
   * to allow the developer to configure properties of, and to return
   * the acceptability of transfers; with a return value of {@code true}
   * indicating that the transfer represented by the given
   * {@code TransferSupport} (which contains all of the details of the
   * transfer) is acceptable at the current time, and a value of {@code false}
   * rejecting the transfer.
   * <p>
   * For those components that automatically display a drop location during
   * drag and drop, accepting the transfer, by default, tells them to show
   * the drop location. This can be changed by calling
   * {@code setShowDropLocation} on the {@code TransferSupport}.
   * <p>
   * By default, when the transfer is accepted, the chosen drop action is that
   * picked by the user via their drag gesture. The developer can override
   * this and choose a different action, from the supported source
   * actions, by calling {@code setDropAction} on the {@code TransferSupport}.
   * <p>
   * On every call to {@code canImport}, the {@code TransferSupport} contains
   * fresh state. As such, any properties set on it must be set on every
   * call. Upon a drop, {@code canImport} is called one final time before
   * calling into {@code importData}. Any state set on the
   * {@code TransferSupport} during that last call will be available in
   * {@code importData}.
   * <p>
   * This method is not called internally in response to paste operations.
   * As such, it is recommended that implementations of {@code importData}
   * explicitly call this method for such cases and that this method
   * be prepared to return the suitability of paste operations as well.
   * <p>
   * Note: The <code>TransferSupport</code> object passed to this method
   * is only valid for the duration of the method call. It is undefined
   * what values it may contain after this method returns.
   *
   * @param support the object containing the details of the transfer, not <code>null</code>.
   * @return <code>true</code> if the import can happen, <code>false</code> otherwise
   * @throws NullPointerException if <code>support</code> is {@code null}
   * @see #importData(TransferHandler.TransferSupport)
   * @see javax.swing.TransferHandler.TransferSupport#setShowDropLocation
   * @see javax.swing.TransferHandler.TransferSupport#setDropAction
   * @since 1.6
   */
  public boolean canImport(TransferSupport support) {
    return support.getComponent() instanceof JComponent
        ? canImport((JComponent) support.getComponent(), support.getDataFlavors())
        : false;
  }

  /**
   * Indicates whether a component will accept an import of the given
   * set of data flavors prior to actually attempting to import it.
   * <p>
   * Note: Swing now calls the newer version of <code>canImport</code>
   * that takes a <code>TransferSupport</code>, which in turn calls this
   * method (only if the component in the {@code TransferSupport} is a
   * {@code JComponent}). Developers are encouraged to call and override the
   * newer version as it provides more information (and is the only
   * version that supports use with a {@code TransferHandler} set directly
   * on a {@code JFrame} or other non-{@code JComponent}).
   *
   * @param comp the component to receive the transfer; provided to enable sharing of
   * <code>TransferHandler</code>s
   * @param transferFlavors the data formats available
   * @return true if the data can be inserted into the component, false otherwise
   * @see #canImport(TransferHandler.TransferSupport)
   */
  public boolean canImport(JComponent comp, DataFlavor[] transferFlavors) {
    PropertyDescriptor prop = getPropertyDescriptor(comp);
    if (prop != null) {
      Method writer = prop.getWriteMethod();
      if (writer == null) {
        // read-only property. ignore
        return false;
      }
      Class<?>[] params = writer.getParameterTypes();
      if (params.length != 1) {
        // zero or more than one argument, ignore
        return false;
      }
      DataFlavor flavor = getPropertyDataFlavor(params[0], transferFlavors);
      if (flavor != null) {
        return true;
      }
    }
    return false;
  }

  /**
   * Returns the type of transfer actions supported by the source;
   * any bitwise-OR combination of {@code COPY}, {@code MOVE}
   * and {@code LINK}.
   * <p>
   * Some models are not mutable, so a transfer operation of {@code MOVE}
   * should not be advertised in that case. Returning {@code NONE}
   * disables transfers from the component.
   *
   * @param c the component holding the data to be transferred; provided to enable sharing of
   * <code>TransferHandler</code>s
   * @return {@code COPY} if the transfer property can be found, otherwise returns <code>NONE</code>
   */
  public int getSourceActions(JComponent c) {
    PropertyDescriptor prop = getPropertyDescriptor(c);
    if (prop != null) {
      return COPY;
    }
    return NONE;
  }

  /**
   * Returns an object that establishes the look of a transfer.  This is
   * useful for both providing feedback while performing a drag operation and for
   * representing the transfer in a clipboard implementation that has a visual
   * appearance.  The implementation of the <code>Icon</code> interface should
   * not alter the graphics clip or alpha level.
   * The icon implementation need not be rectangular or paint all of the
   * bounding rectangle and logic that calls the icons paint method should
   * not assume the all bits are painted. <code>null</code> is a valid return value
   * for this method and indicates there is no visual representation provided.
   * In that case, the calling logic is free to represent the
   * transferable however it wants.
   * <p>
   * The default Swing logic will not do an alpha blended drag animation if
   * the return is <code>null</code>.
   *
   * @param t the data to be transferred; this value is expected to have been created by the
   * <code>createTransferable</code> method
   * @return <code>null</code>, indicating there is no default visual representation
   */
  public Icon getVisualRepresentation(Transferable t) {
    return null;
  }

  /**
   * Creates a <code>Transferable</code> to use as the source for
   * a data transfer. Returns the representation of the data to
   * be transferred, or <code>null</code> if the component's
   * property is <code>null</code>
   *
   * @param c the component holding the data to be transferred; provided to enable sharing of
   * <code>TransferHandler</code>s
   * @return the representation of the data to be transferred, or <code>null</code> if the property
   * associated with <code>c</code> is <code>null</code>
   */
  protected Transferable createTransferable(JComponent c) {
    PropertyDescriptor property = getPropertyDescriptor(c);
    if (property != null) {
      return new PropertyTransferable(property, c);
    }
    return null;
  }

  /**
   * Invoked after data has been exported.  This method should remove
   * the data that was transferred if the action was <code>MOVE</code>.
   * <p>
   * This method is implemented to do nothing since <code>MOVE</code>
   * is not a supported action of this implementation
   * (<code>getSourceActions</code> does not include <code>MOVE</code>).
   *
   * @param source the component that was the source of the data
   * @param data The data that was transferred or possibly null if the action is <code>NONE</code>.
   * @param action the actual action that was performed
   */
  protected void exportDone(JComponent source, Transferable data, int action) {
  }

  /**
   * Fetches the property descriptor for the property assigned to this transfer
   * handler on the given component (transfer handler may be shared).  This
   * returns <code>null</code> if the property descriptor can't be found
   * or there is an error attempting to fetch the property descriptor.
   */
  private PropertyDescriptor getPropertyDescriptor(JComponent comp) {
    if (propertyName == null) {
      return null;
    }
    Class<?> k = comp.getClass();
    BeanInfo bi;
    try {
      bi = Introspector.getBeanInfo(k);
    } catch (IntrospectionException ex) {
      return null;
    }
    PropertyDescriptor props[] = bi.getPropertyDescriptors();
    for (int i = 0; i < props.length; i++) {
      if (propertyName.equals(props[i].getName())) {
        Method reader = props[i].getReadMethod();

        if (reader != null) {
          Class<?>[] params = reader.getParameterTypes();

          if (params == null || params.length == 0) {
            // found the desired descriptor
            return props[i];
          }
        }
      }
    }
    return null;
  }

  /**
   * Fetches the data flavor from the array of possible flavors that
   * has data of the type represented by property type.  Null is
   * returned if there is no match.
   */
  private DataFlavor getPropertyDataFlavor(Class<?> k, DataFlavor[] flavors) {
    for (int i = 0; i < flavors.length; i++) {
      DataFlavor flavor = flavors[i];
      if ("application".equals(flavor.getPrimaryType()) &&
          "x-java-jvm-local-objectref".equals(flavor.getSubType()) &&
          k.isAssignableFrom(flavor.getRepresentationClass())) {

        return flavor;
      }
    }
    return null;
  }


  private String propertyName;
  private static SwingDragGestureRecognizer recognizer = null;

  private static DropTargetListener getDropTargetListener() {
    synchronized (DropHandler.class) {
      DropHandler handler =
          (DropHandler) AppContext.getAppContext().get(DropHandler.class);

      if (handler == null) {
        handler = new DropHandler();
        AppContext.getAppContext().put(DropHandler.class, handler);
      }

      return handler;
    }
  }

  static class PropertyTransferable implements Transferable {

    PropertyTransferable(PropertyDescriptor p, JComponent c) {
      property = p;
      component = c;
    }

    // --- Transferable methods ----------------------------------------------

    /**
     * Returns an array of <code>DataFlavor</code> objects indicating the flavors the data
     * can be provided in.  The array should be ordered according to preference
     * for providing the data (from most richly descriptive to least descriptive).
     *
     * @return an array of data flavors in which this data can be transferred
     */
    public DataFlavor[] getTransferDataFlavors() {
      DataFlavor[] flavors = new DataFlavor[1];
      Class<?> propertyType = property.getPropertyType();
      String mimeType = DataFlavor.javaJVMLocalObjectMimeType + ";class=" + propertyType.getName();
      try {
        flavors[0] = new DataFlavor(mimeType);
      } catch (ClassNotFoundException cnfe) {
        flavors = new DataFlavor[0];
      }
      return flavors;
    }

    /**
     * Returns whether the specified data flavor is supported for
     * this object.
     *
     * @param flavor the requested flavor for the data
     * @return true if this <code>DataFlavor</code> is supported, otherwise false
     */
    public boolean isDataFlavorSupported(DataFlavor flavor) {
      Class<?> propertyType = property.getPropertyType();
      if ("application".equals(flavor.getPrimaryType()) &&
          "x-java-jvm-local-objectref".equals(flavor.getSubType()) &&
          flavor.getRepresentationClass().isAssignableFrom(propertyType)) {

        return true;
      }
      return false;
    }

    /**
     * Returns an object which represents the data to be transferred.  The class
     * of the object returned is defined by the representation class of the flavor.
     *
     * @param flavor the requested flavor for the data
     * @throws IOException if the data is no longer available in the requested flavor.
     * @throws UnsupportedFlavorException if the requested data flavor is not supported.
     * @see DataFlavor#getRepresentationClass
     */
    public Object getTransferData(DataFlavor flavor)
        throws UnsupportedFlavorException, IOException {
      if (!isDataFlavorSupported(flavor)) {
        throw new UnsupportedFlavorException(flavor);
      }
      Method reader = property.getReadMethod();
      Object value = null;
      try {
        value = MethodUtil.invoke(reader, component, (Object[]) null);
      } catch (Exception ex) {
        throw new IOException("Property read failed: " + property.getName());
      }
      return value;
    }

    JComponent component;
    PropertyDescriptor property;
  }

  /**
   * This is the default drop target for drag and drop operations if
   * one isn't provided by the developer.  <code>DropTarget</code>
   * only supports one <code>DropTargetListener</code> and doesn't
   * function properly if it isn't set.
   * This class sets the one listener as the linkage of drop handling
   * to the <code>TransferHandler</code>, and adds support for
   * additional listeners which some of the <code>ComponentUI</code>
   * implementations install to manipulate a drop insertion location.
   */
  static class SwingDropTarget extends DropTarget implements UIResource {

    SwingDropTarget(Component c) {
      super(c, COPY_OR_MOVE | LINK, null);
      try {
        // addDropTargetListener is overridden
        // we specifically need to add to the superclass
        super.addDropTargetListener(getDropTargetListener());
      } catch (TooManyListenersException tmle) {
      }
    }

    public void addDropTargetListener(DropTargetListener dtl) throws TooManyListenersException {
      // Since the super class only supports one DropTargetListener,
      // and we add one from the constructor, we always add to the
      // extended list.
      if (listenerList == null) {
        listenerList = new EventListenerList();
      }
      listenerList.add(DropTargetListener.class, dtl);
    }

    public void removeDropTargetListener(DropTargetListener dtl) {
      if (listenerList != null) {
        listenerList.remove(DropTargetListener.class, dtl);
      }
    }

    // --- DropTargetListener methods (multicast) --------------------------

    public void dragEnter(DropTargetDragEvent e) {
      super.dragEnter(e);
      if (listenerList != null) {
        Object[] listeners = listenerList.getListenerList();
        for (int i = listeners.length - 2; i >= 0; i -= 2) {
          if (listeners[i] == DropTargetListener.class) {
            ((DropTargetListener) listeners[i + 1]).dragEnter(e);
          }
        }
      }
    }

    public void dragOver(DropTargetDragEvent e) {
      super.dragOver(e);
      if (listenerList != null) {
        Object[] listeners = listenerList.getListenerList();
        for (int i = listeners.length - 2; i >= 0; i -= 2) {
          if (listeners[i] == DropTargetListener.class) {
            ((DropTargetListener) listeners[i + 1]).dragOver(e);
          }
        }
      }
    }

    public void dragExit(DropTargetEvent e) {
      super.dragExit(e);
      if (listenerList != null) {
        Object[] listeners = listenerList.getListenerList();
        for (int i = listeners.length - 2; i >= 0; i -= 2) {
          if (listeners[i] == DropTargetListener.class) {
            ((DropTargetListener) listeners[i + 1]).dragExit(e);
          }
        }
      }
      if (!isActive()) {
        // If the Drop target is inactive the dragExit will not be dispatched to the dtListener,
        // so make sure that we clean up the dtListener anyway.
        DropTargetListener dtListener = getDropTargetListener();
        if (dtListener != null && dtListener instanceof DropHandler) {
          ((DropHandler) dtListener).cleanup(false);
        }
      }
    }

    public void drop(DropTargetDropEvent e) {
      super.drop(e);
      if (listenerList != null) {
        Object[] listeners = listenerList.getListenerList();
        for (int i = listeners.length - 2; i >= 0; i -= 2) {
          if (listeners[i] == DropTargetListener.class) {
            ((DropTargetListener) listeners[i + 1]).drop(e);
          }
        }
      }
    }

    public void dropActionChanged(DropTargetDragEvent e) {
      super.dropActionChanged(e);
      if (listenerList != null) {
        Object[] listeners = listenerList.getListenerList();
        for (int i = listeners.length - 2; i >= 0; i -= 2) {
          if (listeners[i] == DropTargetListener.class) {
            ((DropTargetListener) listeners[i + 1]).dropActionChanged(e);
          }
        }
      }
    }

    private EventListenerList listenerList;
  }

  private static class DropHandler implements DropTargetListener,
      Serializable,
      ActionListener {

    private Timer timer;
    private Point lastPosition;
    private Rectangle outer = new Rectangle();
    private Rectangle inner = new Rectangle();
    private int hysteresis = 10;

    private Component component;
    private Object state;
    private TransferSupport support =
        new TransferSupport(null, (DropTargetEvent) null);

    private static final int AUTOSCROLL_INSET = 10;

    /**
     * Update the geometry of the autoscroll region.  The geometry is
     * maintained as a pair of rectangles.  The region can cause
     * a scroll if the pointer sits inside it for the duration of the
     * timer.  The region that causes the timer countdown is the area
     * between the two rectangles.
     * <p>
     * This is implemented to use the visible area of the component
     * as the outer rectangle, and the insets are fixed at 10. Should
     * the component be smaller than a total of 20 in any direction,
     * autoscroll will not occur in that direction.
     */
    private void updateAutoscrollRegion(JComponent c) {
      // compute the outer
      Rectangle visible = c.getVisibleRect();
      outer.setBounds(visible.x, visible.y, visible.width, visible.height);

      // compute the insets
      Insets i = new Insets(0, 0, 0, 0);
      if (c instanceof Scrollable) {
        int minSize = 2 * AUTOSCROLL_INSET;

        if (visible.width >= minSize) {
          i.left = i.right = AUTOSCROLL_INSET;
        }

        if (visible.height >= minSize) {
          i.top = i.bottom = AUTOSCROLL_INSET;
        }
      }

      // set the inner from the insets
      inner.setBounds(visible.x + i.left,
          visible.y + i.top,
          visible.width - (i.left + i.right),
          visible.height - (i.top + i.bottom));
    }

    /**
     * Perform an autoscroll operation.  This is implemented to scroll by the
     * unit increment of the Scrollable using scrollRectToVisible.  If the
     * cursor is in a corner of the autoscroll region, more than one axis will
     * scroll.
     */
    private void autoscroll(JComponent c, Point pos) {
      if (c instanceof Scrollable) {
        Scrollable s = (Scrollable) c;
        if (pos.y < inner.y) {
          // scroll upward
          int dy = s.getScrollableUnitIncrement(outer, SwingConstants.VERTICAL, -1);
          Rectangle r = new Rectangle(inner.x, outer.y - dy, inner.width, dy);
          c.scrollRectToVisible(r);
        } else if (pos.y > (inner.y + inner.height)) {
          // scroll downard
          int dy = s.getScrollableUnitIncrement(outer, SwingConstants.VERTICAL, 1);
          Rectangle r = new Rectangle(inner.x, outer.y + outer.height, inner.width, dy);
          c.scrollRectToVisible(r);
        }

        if (pos.x < inner.x) {
          // scroll left
          int dx = s.getScrollableUnitIncrement(outer, SwingConstants.HORIZONTAL, -1);
          Rectangle r = new Rectangle(outer.x - dx, inner.y, dx, inner.height);
          c.scrollRectToVisible(r);
        } else if (pos.x > (inner.x + inner.width)) {
          // scroll right
          int dx = s.getScrollableUnitIncrement(outer, SwingConstants.HORIZONTAL, 1);
          Rectangle r = new Rectangle(outer.x + outer.width, inner.y, dx, inner.height);
          c.scrollRectToVisible(r);
        }
      }
    }

    /**
     * Initializes the internal properties if they haven't been already
     * inited. This is done lazily to avoid loading of desktop properties.
     */
    private void initPropertiesIfNecessary() {
      if (timer == null) {
        Toolkit t = Toolkit.getDefaultToolkit();
        Integer prop;

        prop = (Integer)
            t.getDesktopProperty("DnD.Autoscroll.interval");

        timer = new Timer(prop == null ? 100 : prop.intValue(), this);

        prop = (Integer)
            t.getDesktopProperty("DnD.Autoscroll.initialDelay");

        timer.setInitialDelay(prop == null ? 100 : prop.intValue());

        prop = (Integer)
            t.getDesktopProperty("DnD.Autoscroll.cursorHysteresis");

        if (prop != null) {
          hysteresis = prop.intValue();
        }
      }
    }

    /**
     * The timer fired, perform autoscroll if the pointer is within the
     * autoscroll region.
     * <P>
     *
     * @param e the <code>ActionEvent</code>
     */
    public void actionPerformed(ActionEvent e) {
      updateAutoscrollRegion((JComponent) component);
      if (outer.contains(lastPosition) && !inner.contains(lastPosition)) {
        autoscroll((JComponent) component, lastPosition);
      }
    }

    // --- DropTargetListener methods -----------------------------------

    private void setComponentDropLocation(TransferSupport support,
        boolean forDrop) {

      DropLocation dropLocation = (support == null)
          ? null
          : support.getDropLocation();

      if (SunToolkit.isInstanceOf(component, "javax.swing.text.JTextComponent")) {
        state = SwingAccessor.getJTextComponentAccessor().
            setDropLocation((JTextComponent) component, dropLocation, state, forDrop);
      } else if (component instanceof JComponent) {
        state = ((JComponent) component).setDropLocation(dropLocation, state, forDrop);
      }
    }

    private void handleDrag(DropTargetDragEvent e) {
      TransferHandler importer =
          ((HasGetTransferHandler) component).getTransferHandler();

      if (importer == null) {
        e.rejectDrag();
        setComponentDropLocation(null, false);
        return;
      }

      support.setDNDVariables(component, e);
      boolean canImport = importer.canImport(support);

      if (canImport) {
        e.acceptDrag(support.getDropAction());
      } else {
        e.rejectDrag();
      }

      boolean showLocation = support.showDropLocationIsSet ?
          support.showDropLocation :
          canImport;

      setComponentDropLocation(showLocation ? support : null, false);
    }

    public void dragEnter(DropTargetDragEvent e) {
      state = null;
      component = e.getDropTargetContext().getComponent();

      handleDrag(e);

      if (component instanceof JComponent) {
        lastPosition = e.getLocation();
        updateAutoscrollRegion((JComponent) component);
        initPropertiesIfNecessary();
      }
    }

    public void dragOver(DropTargetDragEvent e) {
      handleDrag(e);

      if (!(component instanceof JComponent)) {
        return;
      }

      Point p = e.getLocation();

      if (Math.abs(p.x - lastPosition.x) > hysteresis
          || Math.abs(p.y - lastPosition.y) > hysteresis) {
        // no autoscroll
        if (timer.isRunning()) {
          timer.stop();
        }
      } else {
        if (!timer.isRunning()) {
          timer.start();
        }
      }

      lastPosition = p;
    }

    public void dragExit(DropTargetEvent e) {
      cleanup(false);
    }

    public void drop(DropTargetDropEvent e) {
      TransferHandler importer =
          ((HasGetTransferHandler) component).getTransferHandler();

      if (importer == null) {
        e.rejectDrop();
        cleanup(false);
        return;
      }

      support.setDNDVariables(component, e);
      boolean canImport = importer.canImport(support);

      if (canImport) {
        e.acceptDrop(support.getDropAction());

        boolean showLocation = support.showDropLocationIsSet ?
            support.showDropLocation :
            canImport;

        setComponentDropLocation(showLocation ? support : null, false);

        boolean success;

        try {
          success = importer.importData(support);
        } catch (RuntimeException re) {
          success = false;
        }

        e.dropComplete(success);
        cleanup(success);
      } else {
        e.rejectDrop();
        cleanup(false);
      }
    }

    public void dropActionChanged(DropTargetDragEvent e) {
            /*
             * Work-around for Linux bug where dropActionChanged
             * is called before dragEnter.
             */
      if (component == null) {
        return;
      }

      handleDrag(e);
    }

    private void cleanup(boolean forDrop) {
      setComponentDropLocation(null, forDrop);
      if (component instanceof JComponent) {
        ((JComponent) component).dndDone();
      }

      if (timer != null) {
        timer.stop();
      }

      state = null;
      component = null;
      lastPosition = null;
    }
  }

  /**
   * This is the default drag handler for drag and drop operations that
   * use the <code>TransferHandler</code>.
   */
  private static class DragHandler implements DragGestureListener, DragSourceListener {

    private boolean scrolls;

    // --- DragGestureListener methods -----------------------------------

    /**
     * a Drag gesture has been recognized
     */
    public void dragGestureRecognized(DragGestureEvent dge) {
      JComponent c = (JComponent) dge.getComponent();
      TransferHandler th = c.getTransferHandler();
      Transferable t = th.createTransferable(c);
      if (t != null) {
        scrolls = c.getAutoscrolls();
        c.setAutoscrolls(false);
        try {
          Image im = th.getDragImage();
          if (im == null) {
            dge.startDrag(null, t, this);
          } else {
            dge.startDrag(null, im, th.getDragImageOffset(), t, this);
          }
          return;
        } catch (RuntimeException re) {
          c.setAutoscrolls(scrolls);
        }
      }

      th.exportDone(c, t, NONE);
    }

    // --- DragSourceListener methods -----------------------------------

    /**
     * as the hotspot enters a platform dependent drop site
     */
    public void dragEnter(DragSourceDragEvent dsde) {
    }

    /**
     * as the hotspot moves over a platform dependent drop site
     */
    public void dragOver(DragSourceDragEvent dsde) {
    }

    /**
     * as the hotspot exits a platform dependent drop site
     */
    public void dragExit(DragSourceEvent dsde) {
    }

    /**
     * as the operation completes
     */
    public void dragDropEnd(DragSourceDropEvent dsde) {
      DragSourceContext dsc = dsde.getDragSourceContext();
      JComponent c = (JComponent) dsc.getComponent();
      if (dsde.getDropSuccess()) {
        c.getTransferHandler().exportDone(c, dsc.getTransferable(), dsde.getDropAction());
      } else {
        c.getTransferHandler().exportDone(c, dsc.getTransferable(), NONE);
      }
      c.setAutoscrolls(scrolls);
    }

    public void dropActionChanged(DragSourceDragEvent dsde) {
    }
  }

  private static class SwingDragGestureRecognizer extends DragGestureRecognizer {

    SwingDragGestureRecognizer(DragGestureListener dgl) {
      super(DragSource.getDefaultDragSource(), null, NONE, dgl);
    }

    void gestured(JComponent c, MouseEvent e, int srcActions, int action) {
      setComponent(c);
      setSourceActions(srcActions);
      appendEvent(e);
      fireDragGestureRecognized(action, e.getPoint());
    }

    /**
     * register this DragGestureRecognizer's Listeners with the Component
     */
    protected void registerListeners() {
    }

    /**
     * unregister this DragGestureRecognizer's Listeners with the Component
     *
     * subclasses must override this method
     */
    protected void unregisterListeners() {
    }

  }

  static final Action cutAction = new TransferAction("cut");
  static final Action copyAction = new TransferAction("copy");
  static final Action pasteAction = new TransferAction("paste");

  static class TransferAction extends UIAction implements UIResource {

    TransferAction(String name) {
      super(name);
    }

    public boolean isEnabled(Object sender) {
      if (sender instanceof JComponent
          && ((JComponent) sender).getTransferHandler() == null) {
        return false;
      }

      return true;
    }

    private static final JavaSecurityAccess javaSecurityAccess =
        SharedSecrets.getJavaSecurityAccess();

    public void actionPerformed(final ActionEvent e) {
      final Object src = e.getSource();

      final PrivilegedAction<Void> action = new PrivilegedAction<Void>() {
        public Void run() {
          actionPerformedImpl(e);
          return null;
        }
      };

      final AccessControlContext stack = AccessController.getContext();
      final AccessControlContext srcAcc = AWTAccessor.getComponentAccessor()
          .getAccessControlContext((Component) src);
      final AccessControlContext eventAcc = AWTAccessor.getAWTEventAccessor()
          .getAccessControlContext(e);

      if (srcAcc == null) {
        javaSecurityAccess.doIntersectionPrivilege(action, stack, eventAcc);
      } else {
        javaSecurityAccess.doIntersectionPrivilege(
            new PrivilegedAction<Void>() {
              public Void run() {
                javaSecurityAccess.doIntersectionPrivilege(action, eventAcc);
                return null;
              }
            }, stack, srcAcc);
      }
    }

    private void actionPerformedImpl(ActionEvent e) {
      Object src = e.getSource();
      if (src instanceof JComponent) {
        JComponent c = (JComponent) src;
        TransferHandler th = c.getTransferHandler();
        Clipboard clipboard = getClipboard(c);
        String name = (String) getValue(Action.NAME);

        Transferable trans = null;

        // any of these calls may throw IllegalStateException
        try {
          if ((clipboard != null) && (th != null) && (name != null)) {
            if ("cut".equals(name)) {
              th.exportToClipboard(c, clipboard, MOVE);
            } else if ("copy".equals(name)) {
              th.exportToClipboard(c, clipboard, COPY);
            } else if ("paste".equals(name)) {
              trans = clipboard.getContents(null);
            }
          }
        } catch (IllegalStateException ise) {
          // clipboard was unavailable
          UIManager.getLookAndFeel().provideErrorFeedback(c);
          return;
        }

        // this is a paste action, import data into the component
        if (trans != null) {
          th.importData(new TransferSupport(c, trans));
        }
      }
    }

    /**
     * Returns the clipboard to use for cut/copy/paste.
     */
    private Clipboard getClipboard(JComponent c) {
      if (SwingUtilities2.canAccessSystemClipboard()) {
        return c.getToolkit().getSystemClipboard();
      }
      Clipboard clipboard = (Clipboard) sun.awt.AppContext.getAppContext().
          get(SandboxClipboardKey);
      if (clipboard == null) {
        clipboard = new Clipboard("Sandboxed Component Clipboard");
        sun.awt.AppContext.getAppContext().put(SandboxClipboardKey,
            clipboard);
      }
      return clipboard;
    }

    /**
     * Key used in app context to lookup Clipboard to use if access to
     * System clipboard is denied.
     */
    private static Object SandboxClipboardKey = new Object();

  }

}
